Small-Angle X-ray Scattering for PEGylated Liposomal Doxorubicin Drugs: An Analytical Model Comparison Study.

Liposomal delivery systems are recognized as efficient and safe platforms for chemotherapeutic agents, with doxorubicin-loaded liposomes being the most representative nanopharmaceuticals. Characterizing the structure of liposomal nanomedicines in high spatial and temporal resolution is critical to analyze and evaluate their stability and efficacy. Small-angle X-ray scattering (SAXS) is a powerful tool increasingly used to investigate liposomal delivery systems. In this study, we chose a Doxil-like PEGylated liposomal doxorubicin (PLD) as an example and characterized the liposomal drug structure using synchrotron SAXS. Classical analytical models, including the spherical-shell or flat-slab geometries with Gaussian or uniform electron density profiles, were used to model the internal structure of the liposomal membrane. A cylinder model was applied to fit the scattering from the drug crystal loaded in the liposomes. The high-resolution structures of the original drug, Caelyx, and a similar research drug prepared in our laboratory were characterized using these analytical models. The structural parameters of PLDs, including the thickness of the liposomal membrane and morphology of the drug crystal, were further compared. The results demonstrated that both spherical-shell and flat-slab geometries with Gaussian electron density distribution were suitable to elucidate the structural features of the liposomal membrane under a certain range of scattering vectors, while models with uniform electron density distribution exhibited poor fitting performance. This study highlights the technical features of SAXS, which provides structural information at the nanoscale for liposomal drugs. The demonstrated methods are reliable and easy-to-use for the structural analysis of liposomal drugs, which are helpful for a broader application of SAXS in the production and regulation of nanopharmaceuticals.

2D Chiral Stripe Nanopatterns Self-Assembled from Rod-Coil Block Copolymers on Microstripes.

Chiral nanoarchitectures usually possess unique and intriguing properties. However, the construction of 2D chiral nanopatterns through polymer self-assembly is a challenge. Reported herein is the formation of chiral stripe nanopatterns through surface self-assembly of polypeptide-based rod-coil block copolymers on microstripes. The nanostripes align oblique to the boundary of the microstripes, resulting in the chirality of the nanopatterns. The chirality of the nanopatterns is closely related to the width of the microstripes, i.e., a narrower width results in higher chirality. Besides, the chiral sense of the nanopatterns can be regulated by the chirality of the polypeptide blocks. This work demonstrates the transmission of chirality from polymer to nanoarchitecture on a confined surface, which can guide the preparation of nanopatterns with tuned chiral features.

Local Grafting of Ionic Liquid in Poly(vinylidene fluoride) Amorphous Region and the Subsequent Microphase Separation Behavior in Melt.

Polymer-based nanostructures can be generally created by self-assembly of block copolymers that are commonly synthesized by living radical polymerization. In this study, a new strategy is proposed to fabricate block-like copolymers by using the template of binary phase structure of semicrystalline polymers. Poly(vinylidene fluoride) (PVDF) is thermodynamically miscible with an unsaturated ionic liquid (IL) (1-vinyl-3-ethylimidazolium tetrafluoroborate) in the melt and IL molecules are expelled out from the crystalline parts during the crystallization of PVDF. Therefore, the IL molecules are only located at the amorphous region of PVDF crystals. The electron beam irradiation of the IL incorporated PVDF leads to the local grafting of IL molecules onto the PVDF molecular chains in the amorphous region, so block-like grafting polymer chains of crystalline PVDF-b-(amorphous PVDF-g-IL)-b-crystalline PVDF can be achieved. The subsequent heating of the irradiated sample induces the microphase separation of PVDF-g-IL from the ungrafted PVDF chains.

[Study on the Crystal Structure of Cellulose in Bamboo with Synchrotron Radiation Wide Angle X-Ray Scattering].

The crystal structure of cellulose will directly affect the properties of bamboo fiber -reinforced composite, but the unit cell of native cellulose in bamboo has never been investigated. The most accepted model for the structure of native cellulose is Meyer-Misch model which provides a reference to understand the unit cell of native cellulose in bamboo. The native cellulose consists of two different crystal structures (Ⅰ(α) and Ⅰ(ß)) which exist in different plants with different proportions. Because of this situation, the crystal structure of bamboo cellulose should have a unique model. The moso bamboo (Phyllostachys edulis (Carr. ) H. de Lehaie)was selected. The crystal structure of cellulose of bamboo was investigated with two dimensional synchrotron radiation wide angle X-ray scattering (SR-WAXS). The values of the interplanar spacings of each peak were obtained from SR-WAXS patterns, and then crystal structure parameters were calculated according to monoclinic crystal system. The results show that the fibre axis of a bamboo cellulose unit cell with a monoclinic unit cell of a=8.35 Å, b (fiber axis)=10.38 Å, c=8.02 Å, ß=84.99°. This model has a two antiparallel arrangement for the chains in unit cell, with four glucose residues. Thus, the model may be used to provide a theoretical basis for high value-added bamboo fiber -reinforced composite.

Bioinspired Shear-Flow-Driven Layer-by-Layer in Situ Self-Assembly.

Layer-by-layer (LbL) assembly is widely applied as a coating technique for the nanoscale control of architecture and related properties. However, its translational applications are limited by the time-consuming and laborious nature of the process. Inspired by the blood-clotting process, herein, we develop a shear-flow-driven LbL (SF-LbL) self-assembly approach that accelerates the adsorption rate of macromolecules by mechanically configuring the polymer chain via a coil-stretch transition, which effectively simplifies and speeds the diffusion-controlled assembly process. The structural characteristics and surface homogeneity of the SF-LbL films are improved, and diverse three-dimensional structures can be achieved. Functional SF-LbL-assembled surfaces for corneal modification are successfully fabricated, and the surface of wounded rat corneas and skin can be directly decorated in situ with SF-LbL nanofilms due to the advantages of this approach. Furthermore, in situ SF-LbL self-assembly has promise as a simple approach for the wound dressing for interventional therapeutics in the clinic, as illustrated by the successful in situ fabrication of drug-free layers consisting of chitosan and heparin on the dorsal skin of diabetic mice to rescue defective wound healing. This bioinspired self-assembly approach is expected to provide a robust and versatile platform with which to explore the surface engineering of nanofilms in science, engineering, and medicine.